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How to Design a Rock Tumbler

Rock tumblers are simple machines used for creating polished stones from natural stones called rough. In a tumbler, the rough is broken down with naturally abrasive materials, such as sand and metal bits. This process simulates years of wear and tear in about one month. You can purchase a commercial tumbler, or design and make your own out of spare parts. If designing a tumbler, you must include three components into your design: a base, a motor and a barrel.

Things You'll Need

2-by-10 plank
Saw
Ruler
Pencil
Rubber sheet
Scissors
Glue
Barrel
Motor
Drill
Screws
Plywood
4 non-swivel casters with metal housing and rubber wheels
Grit
Rock
Water

Instructions

- 1
  Select a sturdy base that can support the weight of the tumbling barrel, motor and rocks. For example, a 2-by-10 plank provides a base that is stable and portable. Cover the plank with soundproofing foam or rubber to diminish vibrations and cut down on sound. Use screws and waterproof wood glue to secure the soundproofing material.
- 2
  Determine the size of tumbling barrel you need. The volume of the canister limits the amount of rocks that can be tumbled at a single time. Rocks and agitators should fill one-half to three-quarters of the canister. Select either a metal or rubber barrel -- metal barrels last longer but produce more noise. Construct a barrel to meet your specifications or purchase a barrel from a lapidary (rock specialty) supply store.
- 3
  Buy a steel rod that is compatible with the base of the barrel; this rod will connect the barrel directly to the motor.
- 4
  Pick a motor that is powerful enough to rotate your barrel and its load for the required amount of time, keeping in mind that it will run continuously for one to two months. At minimum, buy a 110 volt, 50 cycle, fan-cooled, overload protected motor designed for lapidary use.
- 5
  Determine whether you wish the barrel to rotate in a horizontal or vertical position. Horizontal barrels tumble better but can leak. Upright barrels tumble less effectively but rarely leak.
- 6
  Weld or bolt the steel rod to the motor. Measure the radius of the barrel and add two inches to find measurement "A". Mount the motor above the base at least as high as measurement A. If the barrel is going to be run upright, attach a wooden wedge to the base and then attach the motor to the wedge.
- 7
  Place the empty barrel on the rod. Hold the casters against the base so that the wheels roll in the same direction as the barrel. Place wedges or blocks under the casters to raise them if necessary. Turn the barrel with your hand and make sure that the wheels roll as well. Screw the wheels in place.
- 8
  Test that the unit runs. Fill between one-half and three-quarters of the barrel with rocks, water and grit in the proportions prescribed by the manufacturer of the grit.

Rock Collecting